The present invention relates to an apparatus for correcting surface imperfections such as scratches, dents, bruises, burrs, etc which are caused on a surface of finished gear tooth, and more particularly, to such apparatus for removing and correcting a flaw or bruise, especially one caused by a blow, on a surface of finished gear tooth.
A power transmission gear for use in a machine tool, motor car, etc is generally manufactured by cutting material with a gear cutting machine, then finishing the gear with a grinding machine. At this time, however, burrs would be caused on a tooth surface during a machining operation and bruises from a blow would be caused while a work is carried to the next step, resulting a source of generating a noise while gears are engaged.
Japanese Laid-open Patent Application No. Sho 61-236425 discloses that a gear having only a dedendum such that the diameter of its pitch circle matches an outer diameter of the gear is used as a processing tool, is engaged with a work to be processed by pressing against the latter, and is brought into engaging contact with substantially the entire tooth surface of the work to be processed by relating the processing tool to correct surface imperfections.
In addition, the applicant of the present application has filed Japanese Laid-open Patent Application Sho No. 60-9616 under the title of "an apparatus for burnishing a surface of gear tooth". The outline of this apparatus is shown in FIGS. 5A and 5B.
FIG. 5A shows a state preparatory to operation. Three burnishing gears A, B and C are positioned apart from each other with respect to a work gear W. In FIG. 5B, which shows location of these gears under operation, each of burnishing gears A, B and C goes forward to engage with the work gear W. Under this condition, the center of the burnishing gears A, B and C lies at a respective vertex of an equilateral triangle and the work gear W is evenly pushed by the three burnishing gears A, B and C from three directions. The burnishing gear C is provided with a rotary drive mechanism, so that, in FIG. 5B, with the work gear W is driven by the burnishing gear C.
The burnishing gears A and B are driven by the work gear W, with the result that all the gears can rotate in the directions shown by arrows to remove burrs on a tooth surface of the work gear W and to correct surface imperfections.
In the conventional apparatus described above, it is possible to remove burrs with certainty but it is difficult to certainly correct surface imperfections (such as a flaw from a blow) with certainty. It is believed that this happens because the grinding performance for correcting a flaw from a blow is insufficient when slippage only in one direction is allowed to occur on a tooth surface by pressing the burnishing gears in rotation to a surface flaw having an increased deformation from a blow. For this reason, a portion made defective from a blow is discovered by sound and touch while the work gear is tried on a gear speeder and is manually removed by means of a triangular stick grindstone.
Consequently, while it is possible to reliably correct a flaw from a blow by hand, such correcting operation is time-consuming and with a conventional automated apparatus for correcting a flaw from a blow it is not certain to correct such a flaw.